Week 9 - cerebellum

• cerebellum role is to fine tune your actions making them accurate
• cerebellum has massive cortical area but much simpler then cerebral cortex
• in cerebral cortex there are 6 laminae, cerebellum only 1 output layer
• cerebellum is heavily folded so unfolded is actually very large
• cerebellum exerts influence on movement via MC and PMC as well as connecting with brainstem and spinal cord
• cerebellum adds coordination, fine control, skill to basic movement patterns
• is connected to all cortexes, not just motor
• length of cerebellar cortex reflects body mass and width may effect cognitive properties due to humans having the widest
• molecular layer is at the surface of the cerebellum closest to your skull
• 2 inputs into the cerebellum - climbing and mossy fibres
• 1 output - purkinje cells
• mossy fibres shoot through the purkinje cells and have many connections to them - 200k to each
• climbing fibres wrap around the purkinje cell and only have 1 connection unlike mossy but wrap around the cell causing a lot of power
• parallel fibres shoot through purkinje cells and have many connections to each. Parallel fibres are what make up the 200k connections between mossy and purkinje
• mossy cells connect to the granular cells forming parallel fibres
• Info goes into the purkinje cell and then travels to the cerebellar nuclei before being outputted
• the inhibition from Purkinje cells counteracts any excitatory inputs to the cerebellar nuclei, resulting in a cancellation of net activity.
• hypermetria (overshoot) - finger to nose too long a movement due to poor judgement
• intention tremor - when during an action you cant stop tremoring
• ataxia - loss of coordination and skill
• for the cerebellum to perform purkinje cell activity needs to be reduced to reduce its inhibition allowing the cerebullar nuclei to communicate with the CNS successfully
• purkinje cell activity is reduced through LTD
• the purkinje cell receiving input from both climbing fibres and parallel fibres at the same time this causes the purkinje cell to experience LTD
• the synapse is plastic
• 4 examples of cerebellar learning: 1) vestibular ocular reflex 2) eye blink conditioning 3) skill learning 4) visuo-motor recalibration
• 1. VOR

  
• 2) EB conditioning

  
• 3) skill learning

  
• 4) Visuo-motor recalibration

  
• climbing fibres induce parallel fibre. P cell LTD is the main but not only mechanism for output
• if ball doesnt hit where we wanted we receive an error signal which we use to update motor commands to account for this error next time
• once mistake is made you then have a prediction in mind and compare this to actual sensory feedback in the cerebellum
• cerebellum appears to perform prediction function across different tasks with each being related to this region
• when you make an error in prediction it has been shown there is an increase in cerebellar activity suggesting that prediction errors cause this
• athletes shown to have greater cerebellar grey matter volume due to higher skilled behaviour
• cerebellar specific tasks we actually get better as we get older
• TNS stimulation has been shown to make you learn faster due to LTD
• cerebellum plays a similar role across domains
• results using brain stimulation are difficult to replicate
• parallel and climbing provide excitatory input into purkinje cells which are the output of the cerebellum